Fix display of multiple alerts in home view - Fixes #4757

Copy the logic on grphics/window.py to avoid display more than one
alert at the same time.

Signed-off-by: Gonzalo Odiard <godiard@sugarlabs.org>
Show the Join option in the activity palette in neighborhood - Fixes #4779

The default value when the activity is not configured is 0, not None
Release 0.102.0
Don't let 'Clear Query' override activities preset filters
Don't show 'Clear Query' when the activities preset is active